.\"
.\" Copyright (c) 2000 Dug Song <dugsong@monkey.org>
.\"
.\" $Id: dnet.3 604 2005-02-25 22:59:04Z dugsong $
.\"
.Dd August 21, 2001
.Dt DNET 3
.Os
.Sh NAME
.Nm dnet
.Nd dumb networking library
.Sh SYNOPSIS
.Fd #include <dnet.h>
.Ss Network addressing
.Ft int
.Fn addr_cmp "const struct addr *a" "const struct addr *b"
.Ft int
.Fn addr_bcast "const struct addr *a" "struct addr *b"
.Ft int
.Fn addr_net "const struct addr *a" "struct addr *b"
.Ft char *
.Fn addr_ntop "const struct addr *src" "char *dst" "size_t size"
.Ft int
.Fn addr_pton "const char *src" "struct addr *dst"
.Ft char *
.Fn addr_ntoa "const struct addr *a"
.Ft int
.Fn addr_aton "const char *src" "struct addr *dst"
.Ft int
.Fn addr_ntos "const struct addr *a" "struct sockaddr *sa"
.Ft int
.Fn addr_ston "const struct sockaddr *sa" "struct addr *a"
.Ft int
.Fn addr_btos "uint16_t bits" "struct sockaddr *sa"
.Ft int
.Fn addr_stob "const struct sockaddr *sa" "uint16_t *bits"
.Ft int
.Fn addr_btom "uint16_t bits" "void *mask" "size_t size"
.Ft int
.Fn addr_mtob "const void *mask" "size_t size" "uint16_t *bits"
.Ss Address Resolution Protocol
.Pp
.Li typedef Ar int Fn (*arp_handler) "const struct arp_entry *entry" "void *arg"
.Ft arp_t *
.Fn arp_open "void"
.Ft int
.Fn arp_add "arp_t *a" "const struct arp_entry *entry"
.Ft int
.Fn arp_delete "arp_t *a" "const struct arp_entry *entry"
.Ft int
.Fn arp_get "arp_t *a" "struct arp_entry *entry"
.Ft int
.Fn arp_loop "arp_t *a" "arp_handler callback" "void *arg"
.Ft arp_t *
.Fn arp_close "arp_t *a"
.Ss Binary buffers
.Ft blob_t *
.Fn blob_new "void"
.Ft int
.Fn blob_read "blob_t *b" "void *buf" "int len"
.Ft int
.Fn blob_write "blob_t *b" "const void *buf" "int len"
.Ft int
.Fn blob_seek "blob_t *b" "int off" "int whence"
.Ft int
.Fn blob_index "blob_t *b" "const void *buf" "int len"
.Ft int
.Fn blob_rindex "blob_t *b" "const void *buf" "int len"
.Ft int
.Fn blob_pack "blob_t *b" "const void *fmt" "..."
.Ft int
.Fn blob_unpack "blob_t *b" "const void *fmt" "..."
.Ft int
.Fn blob_print "blob_t *b" "char *style" "int len"
.Ft blob_t *
.Fn blob_free "blob_t *b"
.Ss Ethernet
.Ft eth_t *
.Fn eth_open "const char *device"
.Ft int
.Fn eth_get "eth_t *e" "eth_addr_t *ea"
.Ft int
.Fn eth_set "eth_t *e" "const eth_addr_t *ea"
.Ft ssize_t
.Fn eth_send "eth_t *e" "const void *buf" "size_t len"
.Ft eth_t *
.Fn eth_close "eth_t *e"
.Ss Firewalling
.Pp
.Li typedef Ar int Fn (*fw_handler) "const struct fw_rule *rule" "void *arg"
.Ft fw_t *
.Fn fw_open "void"
.Ft int
.Fn fw_add "fw_t *f" "const struct fw_rule *rule"
.Ft int
.Fn fw_delete "fw_t *f" "const struct fw_rule *rule"
.Ft int
.Fn fw_loop "fw_t *f" "fw_handler callback" "void *arg"
.Ft fw_t *
.Fn fw_close "fw_t *f"
.Ss Network interfaces
.Pp
.Li typedef Ar int Fn (*intf_handler) "const struct intf_entry *entry" "void *arg"
.Ft intf_t *
.Fn intf_open "void"
.Ft int
.Fn intf_get "intf_t *i" "struct intf_entry *entry"
.Ft int
.Fn intf_get_src "intf_t *i" "struct intf_entry *entry" "struct addr *src"
.Ft int
.Fn intf_get_dst "intf_t *i" "struct intf_entry *entry" "struct addr *dst"
.Ft int
.Fn intf_set "intf_t *i" "const struct intf_entry *entry"
.Ft int
.Fn intf_loop "intf_t *i" "intf_handler callback" "void *arg"
.Ft intf_t *
.Fn intf_close "intf_t *i"
.Ss Internet Protocol
.Ft ip_t *
.Fn ip_open "void"
.Ft ssize_t
.Fn ip_add_option "void *buf" "size_t len" "int proto" "const void *optbuf" "size_t optlen"
.Ft void
.Fn ip_checksum "void *buf" "size_t len"
.Ft ssize_t
.Fn ip_send "ip_t *i" "const void *buf" "size_t len"
.Ft ip_t *
.Fn ip_close "ip_t *i"
.Ss Internet Protocol Version 6
.Ft void
.Fn ip6_checksum "void *buf" "size_t len"
.Ss Random number generation
.Pp
.Ft rand_t *
.Fn rand_open "void"
.Ft int
.Fn rand_get "rand_t *r" "void *buf" "size_t len"
.Ft int
.Fn rand_set "rand_t *r" "const void *seed" "size_t len"
.Ft int
.Fn rand_add "rand_t *r" "const void *buf" "size_t len"
.Ft uint8_t
.Fn rand_uint8 "rand_t *r"
.Ft uint16_t
.Fn rand_uint16 "rand_t *r"
.Ft uint32_t
.Fn rand_uint32 "rand_t *r"
.Ft int
.Fn rand_shuffle "rand_t *r" "void *base" "size_t nmemb" "size_t size"
.Ft rand_t *
.Fn rand_close "rand_t *r"
.Ss Routing
.Pp
.Li typedef Ar int Fn (*route_handler) "const struct route_entry *entry" "void *arg"
.Ft route_t *
.Fn route_open "void"
.Ft int
.Fn route_add "route_t *r" "const struct route_entry *entry"
.Ft int
.Fn route_delete "route_t *r" "const struct route_entry *entry"
.Ft int
.Fn route_get "route_t *r" "struct route_entry *entry"
.Ft int
.Fn route_loop "route_t *r" "route_handler callback" "void *arg"
.Ft route_t *
.Fn route_close "route_t *r"
.Ss Tunnel interface
.Pp
.Ft tun_t *
.Fn tun_open "struct addr *src" "struct addr *dst" "int mtu"
.Ft int
.Fn tun_fileno "tun_t *t"
.Ft const char *
.Fn tun_name "tun_t *t"
.Ft ssize_t
.Fn tun_send "tun_t *t" "const void *buf" "size_t size"
.Ft ssize_t
.Fn tun_recv "tun_t *t" "void *buf" "size_t size"
.Ft tun_t *
.Fn tun_close "tun_t *t"
.Pp
.Sh DESCRIPTION
.Nm
provides a simplified, portable interface to several low-level
networking routines, including network address manipulation, kernel
.Xr arp 4
cache and 
.Xr route 4
table lookup and manipulation, network firewalling, network interface
lookup and manipulation, and raw IP packet and Ethernet frame
transmission. It is intended to complement the functionality provided
by
.Xr pcap 3 .
.Pp
In addition, 
.Nm
also provides platform-independent definitions of various network
protocol formats and values for portable low-level network
programming, as well as a simple binary buffer handling API.
.Pp
.Ss Network addressing
Network addresses are described by the following structure:
.Bd -literal
struct addr {
	uint16_t		addr_type;
	uint16_t		addr_bits;
	union {
		eth_addr_t	__eth;
		ip_addr_t	__ip;
		ip6_addr_t	__ip6;
		
		uint8_t		__data8[16];
		uint16_t	__data16[8];
		uint32_t	__data32[4];
	} __addr_u;
};
#define addr_eth	__addr_u.__eth
#define addr_ip		__addr_u.__ip
#define addr_ip6	__addr_u.__ip6
#define addr_data8	__addr_u.__data8
#define addr_data16	__addr_u.__data16
#define addr_data32	__addr_u.__data32
.Ed
.Pp
The following values are defined for
.Ar addr_type :
.Bd -literal
#define ADDR_TYPE_NONE		0	/* No address set */
#define	ADDR_TYPE_ETH		1	/* Ethernet */
#define	ADDR_TYPE_IP		2	/* Internet Protocol v4 */
#define	ADDR_TYPE_IP6		3	/* Internet Protocol v6 */
.Ed
.Pp
The field
.Ar addr_bits
denotes the length of the network mask in bits.
.Pp
.Fn addr_cmp
compares network addresses
.Fa a
and
.Fa b ,
returning an integer less than, equal to, or greater than zero if
.Fa a
is found, respectively, to be less than, equal to, or greater than
.Fa b .
Both addresses must be of the same address type.
.Pp
.Fn addr_bcast
computes the broadcast address for the network specified in
.Fa a
and writes it into
.Fa b .
.Pp
.Fn addr_net
computes the network address for the network specified in
.Fa a
and writes it into
.Fa b .
.Pp
.Fn addr_ntop
converts an address from network format to a string.
.Pp
.Fn addr_pton
converts an address (or hostname) from a string to network format.
.Pp
.Fn addr_ntoa
converts an address from network format to a string, returning a
pointer to the result in static memory.
.Pp
.Fn addr_aton
is a synonym for
.Fn addr_pton .
.Pp
.Fn addr_ntos
converts an address from network format to the appropriate struct
sockaddr.
.Pp
.Fn addr_ston
converts an address from a struct sockaddr to network format.
.Pp
.Fn addr_btos
converts a network mask length to a network mask specified as a struct
sockaddr.
.Pp
.Fn addr_stob
converts a network mask specified in a struct sockaddr to a network
mask length.
.Pp
.Fn addr_btom
converts a network mask length to a network mask in network byte
order.
.Pp
.Fn addr_mtob
converts a network mask in network byte order to a network mask length.
.Ss Address Resolution Protocol
ARP cache entries are described by the following structure:
.Bd -literal
struct arp_entry {
	struct addr	arp_pa;		/* protocol address */
	struct addr	arp_ha;		/* hardware address */
};
.Ed
.Pp
.Fn arp_open
is used to obtain a handle to access the kernel
.Xr arp 4
cache.
.Pp
.Fn arp_add
adds a new ARP
.Fa entry .
.Pp
.Fn arp_delete
deletes the ARP
.Fa entry
for the protocol address specified by
.Fa arp_pa .
.Pp
.Fn arp_get
retrieves the ARP
.Fa entry
for the protocol address specified by
.Fa arp_pa .
.Pp
.Fn arp_loop
iterates over the kernel
.Xr arp 4
cache, invoking the specified
.Fa callback
with each
.Fa entry
and the context
.Fa arg
passed to
.Fn arp_loop .
.Pp
.Fn arp_close
closes the specified handle.
.Pp
.Ss Binary buffers
Binary buffers are described by the following structure:
.Bd -literal
typedef struct blob {
	u_char		*base;		/* start of data */
	int		 off;		/* offset into data */
	int		 end;		/* end of data */
	int		 size;		/* size of allocation */
} blob_t;
.Ed
.Pp
.Fn blob_new
is used to allocate a new dynamic binary buffer, returning NULL on failure.
.Pp
.Fn blob_read
reads 
.Fa len
bytes from the current offset in blob
.Fa b 
into
.Fa buf ,
returning the total number of bytes read, or -1 on failure.
.Pp
.Fn blob_write
writes
.Fa len
bytes from
.Fa buf
to blob
.Fa b ,
advancing the current offset. It returns the number of bytes written,
or -1 on failure.
.Pp
.Fn blob_seek
repositions the offset within blob
.Fa b
to 
.Fa off ,
according to the directive
.Fa whence
(see
.Xr lseek 2
for details), returning the new absolute offset, or -1 on failure.
.Pp
.Fn blob_index
returns the offset of the first occurence in blob 
.Fa b
of the specified
.Fa buf
of length
.Fa len ,
or -1 on failure.
.Pp
.Fn blob_rindex
returns the offset of the last occurence in blob 
.Fa b
of the specified
.Fa buf
of length
.Fa len ,
or -1 on failure.
.Pp
.Fn blob_pack
converts and writes, and
.Fn blob_unpack
reads and converts data in blob
.Fa b
according to the given format
.Fa fmt
as described below, returning 0 on success, and -1 on failure.
.Pp
The format string is composed of zero or more directives: ordinary
characters (not
.Cm %
),
which are copied to / read from the blob, and conversion
specifications, each of which results in reading / writing zero or
more subsequent arguments.
.Pp
Each conversion specification is introduced by the character
.Cm % ,
and may be prefixed by length specifier. The arguments must correspond
properly (after type promotion) with the length and conversion specifiers.
.Pp
The length specifier is either a a decimal digit string specifying the
length of the following argument, or the literal character
.Cm *
indicating that the length should be read from an integer argument for
the argument following it.
.Pp
The conversion specifiers and their meanings are:
.Bl -tag -width indent
.It Cm D
An unsigned 32-bit integer in network byte order.
.It Cm H
An unsigned 16-bit integer in network byte order.
.It Cm b
A binary buffer (length specifier required).
.It Cm c
An unsigned character.
.It Cm d
An unsigned 32-bit integer in host byte order.
.It Cm h
An unsigned 16-bit integer in host byte order.
.It Cm s
A C-style null-terminated string, whose maximum length must be
specified when unpacking.
.El
.Pp
Custom conversion routines and their specifiers may be registered via
.Fn blob_register_pack ,
currently undocumented.
.Pp
.Fn blob_print
prints 
.Fa len
bytes of the contents of blob
.Fa b
from the current offset in the specified
.Fa style ;
currently only
.Dq hexl 
is available.
.Pp
.Fn blob_free
deallocates the memory associated with blob
.Fa b 
and returns NULL.
.Pp
.Ss Ethernet
.Fn eth_open
is used to obtain a handle to transmit raw Ethernet frames via the
specified network
.Fa device .
.Pp
.Fn eth_get
retrieves the hardware MAC address for the interface specified by
.Ar e .
.Pp
.Fn eth_set
configures the hardware MAC address for the interface specified by
.Ar e .
.Pp
.Fn eth_send
transmits 
.Fa len
bytes of the Ethernet frame pointed to by
.Fa buf .
.Pp
.Fn eth_close
closes the specified handle.
.Pp
.Ss Firewalling
Firewall rules are described by the following structure:
.Bd -literal
struct fw_rule {
	char		fw_device[INTF_NAME_LEN]; /* interface name */
	uint8_t		fw_op;			  /* operation */
	uint8_t		fw_dir;			  /* direction */
	uint8_t		fw_proto;		  /* IP protocol */
	struct addr	fw_src;			  /* src address / net */
	struct addr	fw_dst;			  /* dst address / net */
	uint16_t	fw_sport[2];		  /* range / ICMP type */
	uint16_t	fw_dport[2];		  /* range / ICMP code */
};
.Ed
.Pp
The following values are defined for 
.Ar fw_op :
.Bd -literal
#define FW_OP_ALLOW	1
#define FW_OP_BLOCK	2
.Ed
.Pp
The following values are defined for
.Ar fw_dir :
.Bd -literal
#define FW_DIR_IN	1
#define FW_DIR_OUT	2
.Ed
.Pp
.Fn fw_open
is used to obtain a handle to access the local network firewall
configuration.
.Pp
.Fn fw_add
adds the specified firewall
.Fa rule .
.Pp
.Fn fw_delete
deletes the specified firewall
.Fa rule .
.Pp
.Fn fw_loop
iterates over the active firewall ruleset, invoking
the specified 
.Fa callback
with each 
.Fa rule
and the context
.Fa arg
passed to 
.Fn fw_loop .
.Pp
.Fn fw_close
closes the specified handle.
.Pp 
.Ss Network interfaces
Network interface information is described by the following structure:
.Bd -literal
#define INTF_NAME_LEN	16

struct intf_entry {
	u_int		intf_len;		    /* length of entry */
	char		intf_name[INTF_NAME_LEN];   /* interface name */
	u_short		intf_type;		    /* interface type (r/o) */
	u_short		intf_flags;		    /* interface flags */
	u_int		intf_mtu;		    /* interface MTU */
	struct addr	intf_addr;		    /* interface address */
	struct addr	intf_dst_addr;		    /* point-to-point dst */
	struct addr	intf_link_addr;		    /* link-layer address */
	u_int		intf_alias_num;		    /* number of aliases */
	struct addr	intf_alias_addrs __flexarr; /* array of aliases */
};
.Ed
.Pp
The following bitmask values are defined for
.Ar intf_type :
.Bd -literal
#define INTF_TYPE_OTHER		1	/* other */
#define INTF_TYPE_ETH		6	/* Ethernet */
#define INTF_TYPE_LOOPBACK	24	/* software loopback */
#define INTF_TYPE_TUN		53	/* proprietary virtual/internal */
.Ed
.Pp
The following bitmask values are defined for
.Ar intf_flags :
.Bd -literal
#define INTF_FLAG_UP		0x01	/* enable interface */
#define INTF_FLAG_LOOPBACK	0x02	/* is a loopback net (r/o) */
#define INTF_FLAG_POINTOPOINT	0x04	/* point-to-point link (r/o) */
#define INTF_FLAG_NOARP		0x08	/* disable ARP */
#define INTF_FLAG_BROADCAST	0x10	/* supports broadcast (r/o) */
#define INTF_FLAG_MULTICAST	0x20	/* supports multicast (r/o) */
.Ed
.Pp
.Fn intf_open
is used to obtain a handle to access the network interface
configuration.
.Pp
.Fn intf_get
retrieves an interface configuration
.Fa entry ,
keyed on
.Fa intf_name .
For all 
.Fn intf_get
functions, 
.Fa intf_len
should be set to the size of the buffer pointed to by
.Fa entry 
(usually sizeof(struct intf_entry), but should be larger to accomodate
any interface alias addresses.
.Pp
.Fn intf_get_src
retrieves the configuration for the interface whose primary address
matches the specified
.Fa src .
.Pp
.Fn intf_get_dst
retrieves the configuration for the best interface with which to reach
the specified
.Fa dst .
.Pp
.Fn intf_set
sets the interface configuration
.Fa entry .
.Pp
.Fn intf_loop
iterates over all network interfaces, invoking the specified 
.Fa callback
with each interface configuration
.Fa entry 
and the context
.Fa arg
passed to
.Fn intf_loop .
.Pp
.Fn intf_close
closes the specified handle.
.Pp
.Ss Internet Protocol
.Fn ip_open
is used to obtain a handle to transmit raw IP packets, routed by the
kernel.
.Pp
.Fn ip_add_option
adds the header option for the protocol
.Fa proto
specified by
.Fa optbuf
of length
.Fa optlen
and appends it to the appropriate header of the IP packet contained in
.Fa buf
of size
.Fa len ,
shifting any existing payload and adding NOPs to pad the option to
a word boundary if necessary.
.Pp
.Fn ip_checksum
sets the IP checksum and any appropriate transport protocol checksum
for the IP packet pointed to by
.Fa buf 
of length
.Fa len .
.Pp
.Fn ip_send
transmits
.Fa len
bytes of the IP packet pointed to by
.Fa buf .
.Pp
.Fn ip_close
closes the specified handle.
.Pp
.Ss Internet Protocol Version 6
.Fn ip6_checksum
sets the appropriate transport protocol checksum for the IPv6 packet
pointed to by
.Fa buf
of length
.Fa len .
.Pp
.Ss Random number generation
.Fn rand_open
is used to obtain a handle for fast, cryptographically strong
pseudo-random number generation. The starting seed is derived from the
system random data source device (if one exists), or from the current
time and random stack contents.
.Pp
.Fn rand_set
re-initializes the PRNG to start from a known 
.Fa seed
value, useful in generating repeatable sequences.
.Pp
.Fn rand_get
writes 
.Fa len
random bytes into
.Fa buf .
.Pp
.Fn rand_add
adds
.Fa len
bytes of entropy data from
.Fa buf
into the random mix.
.Pp
.Fn rand_uint8 ,
.Fn rand_uint16 ,
and
.Fn rand_uint32
return 8, 16, and 32-bit unsigned random values, respectively.
.Pp
.Fn rand_shuffle
randomly shuffles an array of
.Fa nmemb
elements of 
.Fa size
bytes, starting at
.Fa base .
.Pp
.Fn rand_close
closes the specified handle.
.Pp
.Ss Routing
Routing table entries are described by the following structure:
.Bd -literal
struct route_entry {
	struct addr	route_dst;	/* destination address */
	struct addr	route_gw;	/* gateway address */
};
.Ed
.Pp
.Fn route_open
is used to obtain a handle to access the kernel
.Xr route 4
table.
.Pp
.Fn route_add
adds a new routing table
.Fa entry .
.Pp
.Fn route_delete
deletes the routing table
.Fa entry
for the destination prefix specified by
.Fa route_dst .
.Pp
.Fn route_get
retrieves the routing table
.Fa entry
for the destination prefix specified by
.Fa route_dst .
.Pp
.Fn route_loop
iterates over the kernel
.Xr route 4
table, invoking the specified
.Fa callback
with each
.Fa entry
and the context
.Fa arg
passed to
.Fn route_loop .
.Pp
.Fn route_close
closes the specified handle.
.Pp
.Ss Tunnel interface
.Fn tun_open
is used to obtain a handle to a network tunnel interface, to which
IP packets destined for 
.Fa dst
are delivered (with source addresses rewritten to
.Fa src
), where they may be read by a userland process and processed as
desired. IP packets written back to the handle are injected into the
kernel networking subsystem.
.Pp
.Fn tun_fileno
returns a file descriptor associated with the tunnel handle, suitable
for 
.Xr select 2 .
.Pp
.Fn tun_name
returns a pointer to the tunnel interface name.
.Pp
.Fn tun_send
submits a packet to the kernel networking subsystem for delivery.
.Pp
.Fn tun_recv
reads the next packet delivered to the tunnel interface.
.Pp
.Fn tun_close
closes the specified handle.
.Pp
.Sh RETURN VALUES
.Fn addr_ntop
returns a pointer to the
.Fa dst
argument, or NULL on failure.
.Pp
.Fn addr_ntoa
returns a pointer to a static memory area containing the printable
address, or NULL on failure.
.Pp
.Fn arp_open ,
.Fn eth_open ,
.Fn fw_open ,
.Fn intf_open ,
.Fn ip_open ,
.Fn rand_open ,
and
.Fn route_open
return a valid handle on success, or NULL on failure.
.Pp
.Fn arp_close ,
.Fn eth_close ,
.Fn fw_close ,
.Fn intf_close ,
.Fn ip_close ,
.Fn rand_close ,
and
.Fn route_close
always return NULL.
.Pp
.Fn eth_send
and
.Fn ip_send
return the length of the datagram successfully sent, or -1 on failure.
.Pp
.Fn arp_loop ,
.Fn fw_loop ,
.Fn intf_loop ,
and
.Fn route_loop
return the status of their
.Fa callback
routines. Any non-zero return from a 
.Fa callback
will cause the loop to exit immediately.
.Pp
.Fn ip_add_option
returns the length of the inserted option (which may have been padded
with NOPs for memory alignment) or -1 on failure.
.Pp
.Fn rand_uint8 ,
.Fn rand_uint16 ,
and
.Fn rand_uint32
return 8, 16, and 32-bit unsigned random values, respectively.
.Pp
All other 
.Nm
routines return 0 on success, or -1 on failure.
.Sh SEE ALSO
.Xr pcap 3
.Sh AUTHORS
Dug Song
.Aq dugsong@monkey.org
